DALLAS (CBSDFW.COM) – Dallas-based Southwest Airlines announced Thursday morning that the FAA granted it a single operating certificate for both it and AirTran Airways. It is the FAA’s final approval for the merger of the two airlines.

While the airlines will be allowed to operate as one carrier, Southwest said that both it and AirTran will continue to operate separately. It will take several years, Southwest said, to integrate AirTran’s ticketing system.

AirTran has already pulled out of DFW International Airport, but continues to operate its own airport ticket counters, kiosks and planes in other cities nationwide.

Southwest Airlines spokesman Brad Hawkins said that the airline will completely fold AirTran into Southwest by 2015. That means all of AirTran’s planes will be painted in Southwest’s color scheme, and all AirTran flights and employees will operate under Southwest Airlines.